From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B0F2D3A3E73; Thu, 8 Oct 2026 16:42:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791477750; cv=none; b=DiQahmE5c+/9oJ5YTSx0vWii+mDt9R0iliGuoi6qhfrvyaGnRPVMEyoYRHIYy2hLoGpFAGp0dgQiCOdJp0KrkzayFzpW+Kiu4IbmXExr+Hme9qTnCtPLsfbhYjqoHkHKQV4jw+JT0ty3xxqin7GzMlgwc93gne1Pfm8Fruuo4WU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791477750; c=relaxed/simple; bh=7mvuGWTaFOWJp1wnSmxCGFTK8yaJ6uwg08XxlyeCyKo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=uzDJSUtZASsNwbU1NTNxz/3hcl/Jsi4kelyHnngow9OcRCV+BOTYn+S0Pkd9yemVTx/Ohz0FcH+7zvfn9jLSeFvbQ429OIZz/8dUTblyAht8YLU6K5NfSeCpyyCFANg86Bg8R7tL1ENPl9z1YCZ6KNYxmeNr9nXlTzpuB/rMWXE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=iEZgnBHl; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="iEZgnBHl" Received: from eahariha-devbox.5bhznamrcrmeznzvghz2s0u2eh.xx.internal.cloudapp.net (unknown [20.114.54.184]) by linux.microsoft.com (Postfix) with ESMTPSA id 25BB820B7166; Thu, 8 Oct 2026 09:41:30 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 25BB820B7166 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1791477690; bh=RrdGR8+5+7JD9zLubC3R5Nrwx3f6rQnHI7MHAeeFjZE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iEZgnBHlg1T1yn8CZKhtuBx45f1+HQol4iZG3iM7TQiQXiFIlmf21T9mvH4xgbgRy qUB/J1fkHFphCRL55R8CWqDa4i5ZPlrg3EWE4PLqdRgqrJtOfmoZ39QDPhyiFLR0uK JIx2GA3l12I4vaoXbAFUVMUa5oGTMjpbEw8yJcIw= From: Easwar Hariharan To: jeffbarnes@linux.microsoft.com Cc: Frank.li@oss.nxp.com, Zhiqiang.Hou@nxp.com, bhelgaas@google.com, imx@lists.linux.dev, kwilczynski@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, lpieralisi@kernel.org, mani@kernel.org, minghuan.Lian@nxp.com, mingkai.hu@nxp.com, robh@kernel.org, roy.zang@nxp.com, Easwar Hariharan Subject: [PATCH v2] Revert "PCI: layerscape: Change default error response behavior" Date: Thu, 8 Oct 2026 16:42:02 +0000 Message-ID: <20261008164202.64477-1-easwar.hariharan@linux.microsoft.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261001153323.1965074-1-jeffbarnes@linux.microsoft.com> References: <20261001153323.1965074-1-jeffbarnes@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit > This reverts commit 84d897d69938 > ("PCI: layerscape: Change default error response behavior"). > > The Layerscape PCIe driver programs the DesignWare > AMBA_ERROR_RESPONSE_DEFAULT register at offset 0x8d0 with 0x9401. > > For AXI, the documented default with AMBA_ERROR_RESPONSE_GLOBAL cleared > returns OKAY with all-ones data for errors on non-posted requests. > Setting AMBA_ERROR_RESPONSE_GLOBAL causes an AXI error response instead, > with AMBA_ERROR_RESPONSE_MAP selecting SLVERR or DECERR for individual > PCIe completion errors. > > The value 0x9401 sets AMBA_ERROR_RESPONSE_GLOBAL and maps Unsupported > Request, Completer Abort, and Completion Timeout to SLVERR. > > A PCI configuration access can race with the link going down after > dw_pcie_other_conf_map_bus() checks the link but before > pci_generic_config_read() performs the MMIO access. If the transaction > results in a Completion Timeout, the Layerscape error response setting > propagates it to AXI as SLVERR, resulting in an asynchronous SError and > kernel panic. > Could you bring back the kernel panic backtrace from v1? With that, Reviewed-by: Easwar Hariharan > Reproduce the race by obtaining the configuration-space mapping while > the link is up, then disabling the link from another CPU immediately > before performing the MMIO configuration read. > > With the error response override enabled, the overlapping configuration > read results in an asynchronous SError and kernel panic. With the > DesignWare default behavior restored, the same test returns 0xffffffff. > AER reports a non-fatal Completion Timeout, and no SError or kernel > panic occurs. > > Restore the documented DesignWare default error response behavior so a > failed non-posted PCIe transaction does not become a fatal AXI error. > > Fixes: 84d897d69938 ("PCI: layerscape: Change default error response behavior") > Cc: stable@vger.kernel.org > Signed-off-by: Jeff Barnes > > Changes in v2: > - Change the subject to identify this as a revert, as requested by > Frank Li. > - Document the DesignWare AMBA_ERROR_RESPONSE_DEFAULT behavior and > decode the 0x9401 setting used by Layerscape. > - Clarify that the setting propagates Completion Timeout as AXI SLVERR > rather than causing the underlying PCIe transaction failure. > > --- > drivers/pci/controller/dwc/pci-layerscape.c | 12 ------------ > 1 file changed, 12 deletions(-)